Automotive exhaust gas catalytic converters are commonly used in automobiles to prevent environmental pollution because the catalytic converters greatly reduce air pollutants such as carbon monoxide, nitrogen oxides, etc. without lowering the output and fuel efficiency of the engines.
With recent improvements in the combustion systems in engines, the concentrations of unburned ingredients in exhaust gases have become low. As a result, catalytic converters are now mainly employed. Catalysts for use in these catalytic converters include an oxidation catalyst, a reduction catalyst, and a three-way catalyst, each consisting of a ceramic support of the pellet or monolith-type and a particular catalytic component deposited on the support. Such catalytic components include, for example, noble metals such as Pt, Rh, etc.
Catalytic converters are also used in industrial engines (e.g., engines for use with digestion gases formed by the digestion of organic sludges such as sewage sludges).
However, the known catalytic converters have the following problem. Silicon (including various Si-containing compounds), for example, siloxane gas (Si(CH.sub.3).sub.n O or (CH.sub.3).sub.2 SiO) and phosphorus, for example, phosphoric acid and phosphate (such as H.sub.3 PO.sub.4, HPO.sub.3 and H.sub.4 P.sub.2 O.sub.7) are often present in exhaust gases, mainly because silicones or the like are used in large quantities as sealing materials, i.e., formed in-place gasket (FIPG) for present-day automotive parts and phosphorus is contained in oils. Further, sand and dust, dispersed in the air, may come into the intake air and be introduced into the engine. In the case of engines used with digestion gases, there are also situations where Si etc. enters into the fuel. Because of Si and phosphorous, the noble metals, such as Pt and Rh, used as catalytic components are likely to be poisoned or clogged. This poisoning or clogging greatly impairs the catalyst function.